Use of the cotton swab method in diagnosing Tinea capitis

To evaluate the accuracy of the cotton swab technique for identifying fungal infections of the scalp. The purpose of the study was: 1) to compare the cotton swab technique with the toothbrush method, a popular and reliable means for obtaining specimens; and 2) to ascertain if transport of a specimen, entailing variable transport duration and conditions, impairs the sensitivity and specificity of the technique.

Part 1 consisted of a prospective, investigator-blinded comparison analysis. Fifty children with scalp findings suspicious for tinea capitis were cultured using both techniques: the toothbrush and cotton swab. Ninety-six culture results were obtained for analysis. The second part of the study consisted of a prospective comparison analysis of cotton swab culture results obtained from samples plated immediately after collection in the physician's office as compared with samples transported to outside laboratories for processing. Thirty-one children with presumed tinea capitis were cultured twice with the cotton swab technique; one sample was immediately plated onto fungal medium and the other sent to an outside lab, the selection of which was dictated by the patient's insurance plan. A total of 62 samples were obtained; 58 sample results were used for analysis.

In part 1 of the study, 60% of the 48 children analyzed had positive fungal cultures. Eighty percent of these were Trichophyton species. There was 100% agreement in the results obtained; all patients with positive results using the toothbrush method were also positive when the cotton swab method was used. Similarly, there was complete concordance in laboratory results from the second part of the study. Fifty percent of the 28 children analyzed had positive cultures; 86% grew Trichophyton species. All patients who had positive cultures from those samples plated in-office also had positive results from the outside laboratory samples.

The cotton swab technique is an easy, atraumatic, inexpensive, and reliable means to evaluate patients with suspected tinea capitis. The method remains sensitive and specific even when transport of these specimens is required and processing is thus delayed. This painless technique requires little technical expertise and can be rapidly performed with a standard cotton tip applicator. It should prove an invaluable aid to practitioners in evaluating patients with possible fungal infections of the scalp.